66 Master Cylinder Compensating Port

[Mike S.]

After replacing my nonpower MC with a correct Bendix 3866446, both of my front brakes sometimes begin to drag heavily after brake application. After a few minutes they return to normal. All flexible hoses were replaced at the same time as the MC.

I have read the 66 chassis manual, which instructs MC rebuilders to check the compensating port clearance by inserting a wire. While I can do so on the old MC, I cannot on the new and suspect this is the source of my dragging brakes.

How do I go about adjusting this?

Thanks,

Mike S
#33053

[Mike McKown]

Re: 66 Master Cylinder Compensating Port

Make sure your piston is returning all the way to the snap ring. There is no adjusment feature here.

[Mike S.]

Re: 66 Master Cylinder Compensating Port

Mike -

Apparently the piston is not returning all the way. I've got plenty of free travel in the brake pedal - probably an inch - before the actuating rod contacts the back of the piston.

Could too much free travel be a problem?

[Mike McKown]

Re: 66 Master Cylinder Compensating Port

Mike:

If you have an inch of free play with the new cylinder and not with the old, I would guess your piston is not returning fully, it is stuck in the bore or a wrong piston in the cylinder. Something is definitly wrong if your compensating port is not open.

Take the cylinder off and look at the piston and see if it is seating against the snap ring. If it isn't you can work the piston back and forth and maybe it will free up. I've had this happen on rebuilt cylinders but not new ones. I've also had it happen with silicone fluid but never the glycol.